You could try resetting that gateway device back to factory defaults by using the recessed reset button on the rear. You'll need something like a bent paper clip or a pen tip. Depress and hold it in until you see the front panel indicator lights begin to cycle, then release. Now give it the time it needs to re-sync.
Be advised that if you do this you will wipe out any customized settings that may have been made by you and also lose the wireless security password as well and these will need to be re-done from scratch.